Apex domains cannot have CNAME records.
Question and response
Question
dig d1xn1gjlm4f3wn.cloudfront.net. NS
Answer
d1xn1gjlm4f3wn.cloudfront.net. 5 NS ns-924.awsdns-51.net.
d1xn1gjlm4f3wn.cloudfront.net. 5 NS ns-1573.awsdns-04.co.uk.
d1xn1gjlm4f3wn.cloudfront.net. 5 NS ns-286.awsdns-35.com.
d1xn1gjlm4f3wn.cloudfront.net. 5 NS ns-1458.awsdns-54.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0